Cable boxes receive cable television signals which may be modulated onto any or all of cable channels 2 through 83, and remodulate these signals onto one of channels 2, 3, 4, or 18. In addition, cable channels 84 through 125 are provided for, but are rarely used due to high transmission line losses encountered at high UHF frequencies. In recent years, many television receivers and VCRs have been manufactured to tune both cable and "air" channels. These so-called "cable-ready" or "cable-compatible" units are able to tune through the entire 125 cable channel band. Unfortunately, in order to prevent video piracy, some so-called "premium" channels have been "scrambled" (i.e., encrypted, or encoded) by the cable operator, causing cable boxes to perform a second function, that of descrambler for premium channels.
Many viewers find it desirable to use the tuner of their cable ready television to tune nonscrambled channels directly. This is of great importance when, for example, a viewer wants to record a program from a premium channel while watching a different program on an nonscrambled channel. This can be accomplished by splitting the incoming cable ahead of the cable box and switching the input of the television receiver via a "bypass" switch to the unprocessed (i.e., "raw") cable for the nonscrambled signals, and switching the input of a VCR to the output of the cable decoder box to receive the processed descrambled premium channels. It is common to find directions for such switchable "hook-ups" in the operator's manuals for VCRs and television receivers.
It is in the best financial interest of cable operators to make maximum use of their available spectrum. Thus, in geographic areas in which the cable decoder box is set to provide an output on channel 03, it is quite common to find cable channel 03 occupied. Thus, a user having his television receiver tuned to channel 03, may be watching any cable channel remodulated to channel 03, or in fact, he may be watching cable channel 03 directly via the bypass switch. This is, to say the least, an extremely confusing situation for most nontechnical viewers.
U.S. Pat. No. 4,717,970 (Long), issued 5 Jan. 1988, describes a system which provides to subscribers processed descrambled signals remodulated onto an unused available channel, and unprocessed nonscrambled cable channels. The system of Long eliminates the need for manually-operated video signal switches by providing two parallel signal paths from a signal splitter coupled to a common RF input terminal to signal combiner coupled to a common RF output terminal. The first signal path passes all channels straight through from one output of the splitter to one input of the combiner. The second signal path passes all channels from the other output of the signal splitter to the input of a cable decoder which passes the signal of a selected channel to a modulator which modulates the output signal onto the RF carrier of an unused available channel, preferably a UHF channel. It is herein recognized that Long is not an effective solution to the problem of simplifying cable box operation because Long teaches using an unused available cable channel as the remodulation channel, which is inconsistent with the above-noted, best interest of cable television system operators (i.e., to use as much of their available spectrum as possible, preferably all of it).